use ivreg_dat.dta, clear

ssc install xtivreg2

tsset cowcode year

xtivreg2 cspi v2x_freexp (L.amend23= L.words L.spell_all_amend), fd i(cowcode) t(year) cluster(cowcode) endog(L.amend23)
xtivreg2 cspi v2x_freexp (L.amend3 = L.words L.spell_all_amend), fd i(cowcode) t(year) cluster(cowcode) endog(L.amend3)
